Paradise island threatened by wrecked WWII oil tanker

Video: A trail of bubbles leaking from a sunken tanker indicates that corrosion is worsening

Sixty years on and the impacts of the second world war are still being felt.

A sunken oil tanker, one of dozens on the bottom of Micronesia’s Chuuk Lagoon, is releasing streams of purple diesel bubbles. On 31 July, the resulting oil slick was 5 kilometres long.

Corrosion experts say the 52 wrecks in Chuuk Lagoon could collapse in a few years, yet no-one knows how much fuel was inside the vessels when they sank. The problem could take on astonishing proportions&colon; more than 380 other tankers lie at the bottom of the Pacific.

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Bill Jeffery, a maritime archaeologist at James Cook University in Australia, is part of a team carrying out surveys of the Japanese shipwrecks in the Chuuk Lagoon.

The wrecks are overgrown with coral, house a huge diversity of tropical fish, and attract tourists, who provide welcome income to the local population.

Helped by the charity Earthwatch, the researchers have been studying the site since 2001, so that the Chuukese government can take steps to preserve it.

Growing slick

The teams were told from the start that the wrecks occasionally leaked fuel, which at times washed up on local islands, polluting mangroves. It was originally thought that the leaks were of aviation fuel – some of the sunken ships carried thin drums of fuel to supply Japanese fighter planes in the region.

Jeffery reckons most of the aviation fuel has probably now dissipated into the environment. But three of the 52 wrecks were oil tankers, with a total capacity to carry 32 million litres of fuel – three quarters of what catastrophically leaked from the Exxon Valdez in 1989.

While investigating one of the tankers, the Hoyo Maru, Jeffery and his colleagues came across a 5 kilometre long ribbon of fuel stretching across the lagoon. “We had spotted a small slick in 2007, but this was much bigger,” says Jeffery. “The smell was overpowering.”

During a dive at the wreck, the team traced the ribbon to a steady stream of deep purple bubbles coming out of the tanker’s flank (see video, right).

Collapse danger

“What is frightening is that the Hoyo appears to be leaking from an area where oil was stored,” Jeffery told New Scientist.

Japanese historical records from the time are difficult to come by, so although it had the capacity to carry 15 million litres of oil, at the moment no-one knows how full it was when it sank.

The same holds true for the more than 380 oil tanker wrecks that were mapped by a study published in 2006.

What is certain is that the tankers’ thick hulls will not withstand the bite of saltwater forever. In 2002, Australian corrosion expert Ian MacLeod assessed the Chuuk shipwrecks and concluded that some could start to collapse within 10 to 15 years. Subsequent assessments over the last three years have confirmed his conclusion.

Nor is the Hoyo Maru the only ship to be leaking oil – although for now, it is the only tanker which has been seen to leak.

Footing the bill

The same week the team found the Hoyo Maru leak, two Earthwatch volunteers noticed a smaller cluster of fuel bubbles coming out of the Rio de Janeiro Maru, a passenger vessel that was converted to lend support to Japanese submarines during the war.

Jeffery and his colleagues are now seeking Japanese historians and shipping experts who could remotely assess the contents of the Hoyo’s oil storage tanks. If the ship is found to contain large amounts of diesel, this will need to be pumped out in order to avoid severe damage to the local biodiversity and economy.

It is not clear who will foot the bill. The vessels are Japanese but in foreign territory, and the Chuukese government is unlikely to have sufficient funds.

The situation is likely to repeat itself around the Pacific over coming years. “A lot of these wrecks are in areas where the communities just don’t have the resources to deal with oil pollution,” warns Jeffery.